<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div>
  <button id="btn"></button>
</div>
<script>
  let btn = document.querySelector('#btn')
  btn.addEventListener('click',function () {

  })
</script>
</body>
</html>